This invention relates to an improved intravascular catheter and in particular to an improved intravascular catheter that can have a very low profile and that allows for the exchange of a first catheter for another catheter over a guide wire, and methods for use thereof.
Intravascular catheterization apparatuses have proven to be useful and efficient for both therapeutic and diagnostic purposes. Intravascular catheterization therapies, such as angioplasty, atherectomy, and laser irradiation, have been developed as alternatives to bypass surgery for treating vascular diseases or other conditions that occlude or reduce the lumen size of portions of a patient's vascular system. In particular, balloon angioplasty has proven to be a useful and in many circumstances a preferred treatment for obstructive coronary diseases. Also, intravascular diagnostic catheter apparatuses, for angiographics, ultrasonic imaging, and Doppler blood flow measurements for example, have been developed to measure or image the extent of an occlusion of a vessel, (e.g., stenosis). These intravascular diagnostic apparatuses may be used in conjunction with the aforementioned therapeutic apparatuses or may be used in conjunction with more invasive techniques such as coronary surgery.
These intravascular therapeutic and diagnostic apparatuses have achieved acceptance because of their effectiveness as well as the fact that they can be used through a minor surgical procedure that is relatively non-disruptive to the patient compared to coronary surgery. These intravascular therapeutic and diagnostic apparatuses rely on the positioning of a catheter device into the vascular system of a patient via an incision at an accessible location which may be remote from the site of the occlusion or stenosis. For example, the accessible location may be the femoral artery at the groin. The intravascular device is then advanced through the incision via the femoral artery to the desired coronary distal site.
Because of the small size of some of these vessels and the tortuous passages through the vessels, positioning of a catheter device through a patient's vasculature can be a difficult and time consuming task requiring considerable skill on the part of the physician. For example, in order to perform an angioplasty dilation, the angioplasty balloon catheter must be positioned across the stenosis in the arterial site. The stenosis may be located in a tortuous portion of the coronary vasculature and, furthermore, the obstructive arterial disease may impede crossing the stenosis with the balloon portion of the angioplasty catheter. Thus, not all arterial obstructions can be successfully treated by present intravascular balloon catheter procedures because some arterial obstructions are not readily accessible to a balloon dilation catheter. Accordingly, there is a need for intravascular catheters of very low profile that can be positioned in narrow, tortuous regions of a person's vasculature.
Another important consideration relating to intravascular procedures, such as angioplasty, relates to catheter exchanges. Intravascular therapeutic and diagnostic devices come in various types and sizes suitable for the vessel size and location in which the treatment is to be performed. Sometimes, it becomes necessary to exchange a first therapeutic device for one of a different size after the first device has been positioned or after an unsuccessful attempt to position the first device. This may be necessitated because it becomes apparent that the first device is the wrong size or because it is determined that additional therapeutic or diagnostic procedures with a different size or type of device is required.
Several different types of catheter constructions have been developed for positioning intravascular therapeutic or diagnostic catheters through a patient's vasculature. One type of catheter design, commonly referred to a fixed-wire type catheter, includes a non-removable wire tip attached on a distal end of the intravascular catheter. The wire tip facilitates maneuvering the catheter to the desired vessel site. A disadvantage of the fixed-wire type catheter that is if it becomes necessary to exchange a first catheter for a second catheter, the maneuvering procedure must be repeated for the second catheter. As mentioned above, this can be sometimes a tedious and difficult procedure.
Another type of catheter design, referred to as an over-the-wire type catheter, includes a central lumen through the intravascular device that can accommodate a separate guide wire that is movable, and removable, in relation to the catheter to facilitate positioning the catheter in a remote vessel location over the guide wire. In the over-the-wire construction, the catheter includes a lumen adapted to receive the guide wire from a proximal end to the distal end of the device. The guide wire is initially loaded through the lumen of the over-the-wire catheter and extends out from the distal end thereof. Then, the guide wire and the intravascular catheter are advanced together and positioned in the vessel at the desired site. The guide wire may be advanced distally of the distal end of the catheter and steered, as necessary, to traverse tortuous passages of the vessel. The guide wire may then be withdrawn proximally through the lumen of the catheter or may be left in place extending from the distal end of the catheter during the procedure.
The over-the-wire type catheter facilitates exchanges. In order to exchange a first over-the-wire intravascular catheter with another, it is preferred not to lose a hold on the proximal end of the guide wire as the catheter is withdrawn over the proximal end of the guide wire. An intravascular catheter with an over-the-wire construction can be exchanged while leaving the distal tip of the guide wire in place by using an exchange wire which is a guide wire having a long length (e.g. 300 cm) so that a sufficiently long proximal portion of the guide wire extends out of the proximal end of the catheter so that the entire catheter can be withdrawn out completely over the wire while maintaining a hold on a proximal portion of the wire. Another way to perform an exchange with an over-the-wire type intravascular catheter is by using a guide wire extension.
A variation of the over-the-wire type catheter that facilitates exchange of a first intravascular catheter with another is the single-operator exchange type design construction. With the single-operator construction, the guide wire occupies a position adjacent to the intravascular catheter along proximal and middle portions of the catheter and enters into a short guide wire lumen of the catheter via an opening in the catheter at a location in a distal portion of the catheter. With this type of design, the catheter can be positioned in the patient's vessel by positioning a guide wire in the desired location and advancing the catheter device over the wire. However, in the event that it becomes necessary to exchange the single-operator catheter, the catheter can be withdrawn proximally while the distal tip of the guide wire is left in position in the vessel site. Because the proximal end of the guide wire and the proximal end of the catheter are adjacent to each other, the proximal end of the guide wire can be held so that the position of the distal end of the guide wire in the patient's vessel can be maintained. With this type of catheter, it is necessary that the distance from the distal end of the catheter to the proximal guide wire lumen entrance is less than the length of the guide wire that extends proximally out of the guiding catheter.
Although intravascular catheters, such as the over-the-wire type and the single-operator type, that employ a separate guide wire provide advantages relating to exchanges, these types of catheters obtain this advantage at the expense of size. In order to accommodate the separate guide wire, a separate guide wire lumen must be provided through at least a portion of the catheter. This element unavoidably increases the overall dimensions of the catheter to at least some degree compared to the fixed-wire type catheter.
Accordingly, there is a need for an improved balloon dilation catheter that facilitates catheter exchange over a guide wire, but that can possess the very small profile of a fixed-wire type catheter.